On the α → β Transition of Carbon-Coated Highly Oriented PVDF Ultrathin Film Induced by Melt Recrystallization

Recovery of remanent polarization of poly(vinylidene fluoride-co-trifluoroethylene) thin film after high temperature annealing using topographically nanostructured aluminium bottom electrode

“…11 In our system, the similar behavior may occur in very thin P͑VDF-TrFE͒ layer bound onto the topographic and periodic nanostructure of an etched Al upon melt and recrystallization. The ultrathin effective layer, which has the memory of the crystal orientation before melting near the etched Al electrode surface, is speculated to facilitate the reorganization of crystal to its b axis perpendicular to the etched Al substrate under the low electric field, leading to the fairly large polarization.…”

“…12 The crystal memory effect that the orientation of a polymer crystal obtained by fabrication process below T m reappears even after melting, and recrystallization has been reported in many different semicrystalline polymers. 11,13,14 When the experimental temperature for polymer crystal melting is not sufficiently high above its T m , amorphous polymer chains stay near the place originally located in the crystalline lamellae due to the lack of chain mobility. The subsequent crystallization makes the chains form crystal lamellae with the orientation similar to one before melting.…”

Spin cast ferroelectric beta poly(vinylidene fluoride) thin films via rapid thermal annealing

“…In spite of a number of methods to achieve the ␤ crystals of several micron thick PVDF films that include mechanical stretching, electric poling, hygroscopic salts, epitaxy with KBr and rate of cooling and heating, and solvent evaporation, [4][5][6] only few works have dealt with the polymorphic transition in thin PVDF films less than 300 nm in thickness with the low operating voltage of less than 30 V. A recent work by Wang et al 7 demonstrating ultrathin meltdrawn ␤ PVDF film seems hardly useful for devices due to nonuniformity of the film. From the industrial point of view, therefore, spin coating is one of the most desirable methods for large area uniform film formation.…”

Recent Development in Polymer Ferroelectric Field Effect Transistor Memory

“…Most of works have focused on methods to achieving polar β structure in several micron thick films that are rarely applicable for memory device due to substantially high operating voltage of more than 100 V. The methods include mechanical stretching, high compression, hygroscopic salts and rate of cooling and heating, solvent evaporation [54]. One should, therefore, find a way based on spin casting process to fabricate polar ferroelectric thin PVDF films of less than 200 nm in thickness that are suitable for reasonably low operating voltage of approximately 10 V. A recent work by Wang et al has proposed a method for fabricating ultra thin melt-drawn film with β crystals by melting and recrystallization under carbon evaporated surface [55]. From the industrial point of view, spin coating is one of the most desirable methods for large area uniform film formation and thus provides a great benefit when it is incorporated in fabricating PVDF based devices.…”